package parser

import "github.com/mmakaay/toml/parsekit"

// There are four ways to express strings: basic, multi-line basic, literal,
// and multi-line literal. All strings must contain only valid UTF-8 characters.
// * Multi-line basic strings are surrounded by three quotation marks on each side.
// * Basic strings are surrounded by quotation marks.
func startString(p *parsekit.P) {
	switch {
	case p.After(doubleQuote3).Ignore():
		p.RouteTo(startMultiLineBasicString)
	case p.After(doubleQuote).Ignore():
		p.RouteTo(startBasicString)
	default:
		p.UnexpectedInput("a string value")
	}
}

// For convenience, some popular characters have a compact escape sequence.
//
// \b         - backspace       (U+0008)
// \t         - tab             (U+0009)
// \n         - linefeed        (U+000A)
// \f         - form feed       (U+000C)
// \r         - carriage return (U+000D)
// \"         - quote           (U+0022)
// \\         - backslash       (U+005C)
// \uXXXX     - unicode         (U+XXXX)
// \UXXXXXXXX - unicode         (U+XXXXXXXX)
//
// Any Unicode character may be used except those that must be escaped:
// quotation mark, backslash, and the control characters (U+0000 to U+001F, U+007F).
func parseBasicString(p *parsekit.P) {
	switch {
	case p.AtEndOfFile():
		p.UnexpectedEndOfFile("basic string token")
	case p.After(backslash, validEscapeChars).Store() ||
		p.After(shortUtf8Match).Store() ||
		p.After(longUtf8Match).Store():
		p.RouteRepeat()
	case p.After(mustBeEscaped).Backup():
		r, _, _ := p.Match(mustBeEscaped)
		p.EmitError("Invalid character in basic string: %q (must be escaped)", r[0])
	case p.After(backslash).Backup() || p.After(doubleQuote).Backup():
		p.RouteReturn()
	default:
		p.AcceptAny()
		p.RouteRepeat()
	}
}

func startBasicString(p *parsekit.P) {
	p.RouteTo(parseBasicString).ThenTo(basicStringSpecifics)
}

// Specific handling of input for basic strings.
// * A double quote ends the string
// * No additional \escape sequences are allowed. What the spec say about this:
//   "All other escape sequences [..] are reserved and, if used, TOML should
//    produce an error.""
func basicStringSpecifics(p *parsekit.P) {
	switch {
	case p.After(doubleQuote).Ignore():
		if err := p.EmitInterpreted(ItemString); err != nil { // TODO testcase?
			p.EmitError("Invalid data in string: %s", err)
		} else {
			p.RouteTo(startKeyValuePair)
		}
	case p.After(backslash).Backup():
		p.EmitError("Invalid escape sequence")
	default:
		p.RouteTo(startBasicString)
	}
}

func startMultiLineBasicString(p *parsekit.P) {
	p.EmitError("Not yet implemented")
}